Coal tar paving compositions and process for preparing them



tes atet Patented Feb. 14, 1967 3 304,191 COAL TAR PAVIbiG COMPOSITIGNS AND PROCESS FOR PREPARING THEM Richard C. Barrett, New Milford, N..l., assignor to Allied Chemical Corporation, New York, N.Y., a corporation of New York No Drawing. Filed May 21, 1963, Ser. No. 282,143

5 Claims. (Cl. 106279) This invention relates to improved coal tar compositions adapted for use as paving binders, and to a process for preparing them.

Bituminous materials have been used for many years in the preparation of road paving compositions to bind mineral aggregate in the roadbed or other paved areas and to present a smooth and durable wearing surface for traffic.

Bituminous binders of two main type sare used in paving operations. The most widely used are the asphalts, derived as residues from asphaltic petroleumisi. The petroleum asphalts are normaly solid, or semi-solid bitumens, which are usually applied to the road or other similar surface or to mineral aggregate either in the hot molten state or as solutions in volatile solvents. Such compositions then set or solidify, either rapidly, by cooling or, more slowly, by evaporation of the volatile solvent, thus producing firm surfaces which are little affected by temperature changes which occur in normal outdoor exposure, resulting in surfaces possessing low temperature suceptibilities. The petroleum asphalts, in general, however, suffer both from poor initial wetting power for the mineral aggregate used in pavement construction which results in poor binding of the aggregate mass. They also suffer from poor water resistance, so that when exposed to water they tend to disengage from the aggregate. The asphaltic bitumens, moreover, are completely soluble in petroleum oils and greases and, thus, surfaces composed of such binders suffer serious damage when exposed to such petroleum products, as for example, to jet fuel, gasoline or motor oil and the like.

Also used as bituminous paving binders are certain tarry residues obtained in the distillation of crude tars resulting from the destructive distillation of bituminous coal, the principal source of such tar being the by-product coke ovens producing metallurgical coke. Such residues may be, and usualy are, cut back or fluxed, before use, with coal tar distillates to meet the required specifications for the desired type of tar. Standard road tars are customarily prepared in fourteen different grades, which are essentially similar except for differences in consistency or viscosity, the variety of grades being provided so that material may be chosen to meet local conditions of temperature, road conditions, climate, etc. Specifications for such tars are given in ASTM specification D-490. The lower numbered grades RT-l, RT-2, RT-3 and RT-4, are relatively low viscosity tars used in general in prime coat application and light surface treatment of pavements; RT-S and RT-6 are of somewhat higher consistency and serve for use in surface treatment and road mix; RT-7, RT-8 and RT9 of still higher consistencies, are useful in surface treatment, road mix, plant mix and seal coats, these latter grades being the most Widely used and representative grades of road tars; RT-lt), RT-ll and RT-12 of even higher consistencies are for use in surface treatment, plant mix, penetration, crack filler and seal coat aplications, while the special grades RT CB5 and RT CB-6 of consistencies similar to the RT-S and RT6 grades but somewhat quicker setting, are used in patching, surface treatment and also for plant mix and road mix where low temperature application and quick setting are desired.

All these coal tar derived road tars have superior wetting power for mineral aggregate and are extremely resistant to both water and to petroleum oils and greases. The coal tars, however, lack the low temperature susceptibility of the petroleum asphaltic bitumens, and tend to flow and bleed out of the aggregate when used in paving construction.

The asphalt type binders uesd in road and similar constructions are essentially non-volatile and are ordinarily applied as hot melts or as solvent solutions. When hotapplied, these materials set by cooling and undergo no further change in physical characteristics. When applied as a solution in a solvent the binder cures by solvent evaporation and leaves a residual film of the non-volatile asphalt.

The coal tar binders, in contrast, are composed of a multiplicity of components with varying degrees of volatility. Although often heated to increase fluidity for application, they are not initially solid at normal temperature, and harden or cure by the slow progressive evaporation of the more volatile portions of the tar itself. When attempts are made to hasten the curing time by increasing the amount of the more volatile component there must also be an increase in the hard non-volatile component if the desired viscosity is to be retained. The non-volatile pitch constituents of coal tar have a high temperature susceptibility and thus such a blend, while having a satisfactory cure rate will leave a residual binder highly susceptible to changes in consistency with changes in temperature.

An object of the present invention is to provide a paving composition composed entirely of coal tar derived components, which has an unusually low temperature susceptibility and an exceptionally fast rate of curing when applied to road or other surfaces.

These and other objects are accomplished by the new compositions of my invention comprising mixtures of normal road tars with between about 25% and about by volume of an oxidized aromatic flux oil residue, as hereinafter defined, fluxed with sufiicient quantities of a coal tar distillate fiuxing oil to meet the requirements of ASTM specifications D-490.

The coal tar paving compositions of my invention are suitable for use in all types of paving applications, for example, in the preparation of bituminous macadam, bituminous concrete, in cover coats and in the preparation of the so-called black bases. The advantages of these black bases have recently been demonstrated by road tests conducted by the American Association of State Highway Officials. Black bases are pre-mixed blends of run-ofbank gravel of the desired size, with bituminous paving compositions. Such bases are applied alone or in combination with penetration macadam to the sub-base of the area to be paved.

Use of these black bases has been found to yield economic advantages in that they require lower coat thicknesses to provide the same load bearing capacity, than are required of the standard penetration macadam or bituminous concrete. The greater the load bearing capacity of the black base, the thinner the layer that can be applied to produce the same durability in the paving. These black bases, moreover, are customarily stock piled at the job site in advance of starting construction so that for such black bases, it is important that the tar used in their preparation be selected to preserve the workability of the base over the period of storage.

Besides meeting all the requirements of the ASTM standards, the paving compositions of my invention all have unusually low temperature susceptibilities, fast curing rates, and yield residues of controlled high softening points.

Temperature susceptibility, as used in the bituminous paving art, refers to the change in consistency of the composition with temperature. Thus a composition which is hard at low temperatures may soften rapidly as temperature is raised. Such a composition is said to have a high temperature susceptibility. A composition with a low temperature susceptibility, on the other hand, will not soften as rapidly with rises in temperature and will not harden as rapidly with reductions in temperature. This susceptibility to changes in consistency with tempera ture may be rated by the correlation of the needle penetration at a given temperature, usually at 77 F., to the ring and ball softening point of the bitumen. A common and useful method of correlating these values is by the so-called Penetration Index, as defined in the publication entitled, Classifying Asphalts by Means of Penetration Index, by J. Ph. Pfeifier and P. M. Van Doormal which appeared in the February 23, 1938 issue of National Petroleum News, pages R-78 to R-84.

In that publication a nomograph is provided relating penetration to ring and ball softening temperature, from which a penetration index value may be derived which is a valuable index of temperature susceptibility of the bitumen. The temperature susceptibility scale as shown in the publication ranges from minus 10 to plus 20. An index of +20 would indicate zero temperature susceptibility. With increasing susceptibility the index decreases through to 10, the latter value corresponding to an infinitely large susceptibility. Thus the lower the penetration index, the higher is the temperature susceptibility of the bitumen.

Penetration indexes of normal coal tar based road tars meets the ASTM specifications usually range substantially below -1.5 usually close to -2, and hence are rated as having high temperature susceptibility, i.e., poor resistance to temperature change. By the incorporation of substantial proportions of oxidized aromatic flux oil as defined, in normal road tar, the penetration index is significantly raised to values above 2.0, usually to values between about 1.5 and about 1.0 or higher.

The term curing rate refers to the rate of gradual hardening or setting of the tar, after application to the surface, which takes place by evaporation of volatile matter in the tar. This rate depends on a number of factors, including the relative proportions of components of different boiling points, ambient temperatures during the successive stages of cure, etc. A rapid cure to the consistency required to minimize bleeding or flow and to sustain traffic is desirable.

As a measure of curing rate, ASTM specification D- 490 requires that the residue produced by distilling the road tar to 300 C. according to ASTM test method D-20 shall have a ring and ball softening point between 30 C. and 70 C., the tars of higher residue softening point values being the faster curing. The precise range varies slightly for the different grades of tar. As a practical matter the majority of road tars have residue softening points of around 40 to 45, and thus have relatively low curing rates. While it is possible to produce a normal road tar having high residue softening points up to the 70 C. maximum or higher by the simple expedient of removing some of the lower boiling components of the tar by distillation to a high melting point residue and then diluting or cutting back the tar with a volatile solvent, the resulting residues as deposited on the road or other surface have excessively high temperature susceptibilities and are subject to embrittlement on cooling to normal ambient temperatures and below.

The tars of the present invention, on the other hand, have residue softening points in the upper portion of the ASTM-D-490 specification range, i.e. between about 50 C. and about 70 C. and still provide residues having a low degree of temperature susceptibility as pointed out above. Thus the tars of my invention possess concomitantly the two heretofore-considered paradoxical properties of fast cure and low temperature susceptibilities rendering them of exceptional value particularly in a number of specialized applications as brought out above.

While the ring and ball softening point of the D2O distillation residue, obtained as outlined above, is indicative of the relative curing rates to be expected of normal tars as presently formulated, the test fails to simulate actual curing conditions by so great a measure that it might be possible to prepare a tar which would meet the above tests but which still would not cure properly, when deposited on the road or other surface. To meet this deficiency and to provide a definitive test which more accurately reflects the actual behavior of the tar when exposed to atmospheric conditions on the road, or other surface, an accelerated test has recently been devised to measure curing rates which can be expected of tars under normal conditions on a road or other surface. This test involves applying a uniform, thin film of the tar of standard thickness, usually 0.032 inch, to a plane surface, and subjecting the films to simulated aging conditions by exposure to 50 C. (122 F.) temperature under forced air circulation conditions, and measuring the ring and ball softening points of the films at successive intervals. In this way a definitive and substantially reliable comparison of relative curing times of different tars can be obtained.

The oxidized aromatic flux oil residue which is the critical component of the new paving tars of my inven tion, is obtained by subjecting a selected coal tar flux oil to intimate contact with a gas containing elemental oxy" gen, for example air, at temperatures between about 200 C. and about 500 C. for a time sufficient to produce an oxidized fiux oil residue containing at least about 15%, preferably between about 15% and about 45% by weight of benzol-insoluble compounds, usually about 30%. The oxidized aromatic flux oil residue is a pitch-like material having a ring and ball softening point between about 50 C. and about 135 C., preferably between about 60 C. and about C. and a Penetration Index between 0 and 1.5, usually about -0.5. The oxidized product has a specific gravity, Sp. Gr. 25/ 25 C., between 1.20 and 1.25, usually about 1.22. As noted above, the flux oil after oxidation, no longer is an oil but has substantially the characteristics of a pitch. Blowing the flux oil under the above conditions gives rise to formation of benzol-insoluble compounds which are believed to be responsible for the improved characteristics of reduced temperature susceptibilities in the residues from the blended tars containing the oxidized aromatic flux oil residue. Quinoline-insolubles, on the other hand, are not formed in this treatment, and so are present in the treated residue in proportions of not more than about 5%.

The selected flux oils from which the oxidized product is derived, are distillate oils obtained in the distillation of tars resulting from the destructive distillation of bituminous coals. These oils boil above about 250 C. under standard conditions, and usually comprise the so-called light and heavy tar oil fractions, and may also include residues from vredistillation of lighter distillate fractions.

Proportions of the oxidized aromatic flux oil residue as defined, up to 75 by volume based on the volume of the normal road tar/air-blown flux oil blend may be used. I have found that higher proportions of oxidized aromatic flux oil residue tend to cause crystallization of the resulting film when applied to the surface and, in the higher consistency grades (RT-7 to RT-12), prevent compliance with the ASTM float test requirement due to this crystallization tendency. Even small proportions of the oxidized aromatic flux oil residue added to normal road tars improve the temperature susceptibility and cure of the resulting blend. However, I usually prefer to use at least about 25% of oxidized aromatic flux oil residue with 75% tar, percentages between about 50% and about 75 based on the oxidized aromatic flux oil residue/normal tar blend being preferred;

The blends of oxidized aromatic flux oil residue with normal tar are then cut back with a suitable fiuxing agent to the consistency desired. Suitable fluxing agents are those in the nature of the so-called light carbolic oil residue (LCOR) which is a coal tar fraction boiling pri- (ring and ball) and penetration with the following results, shown in Table II below.

manly (85% dry) between about 235 C. and about A LE II 315 C., suitably having a specific gravity, Sp. Gr. 25/25 5 RT-S Ex. 1 Ex. 2

C., between about 1.040 and about 1.060, usually obtained, as the name implies, as a residue from distillation ggr nz 13 T 100 67 40.5

of the light carbolic oil fraction of the coal tar. Other a i fi ifiifi l? coal tar derived fluxing agents may also be used having %3 1M 19 the same general character as the light carbolic oil residue, 0-300: (5. 2

for example, a similar oil which may be obtained as the 832%.. 8: M2 2? distillate produced by stripping creosote oil to a vapor R s du W ight Percent 75.5 73.5 74.1

temperature of 300 C., 0r if desired, a mixture of Creo- P ef i f gigfiyggiiffiif 2 O 3 ene ra ion a g. 5 sec 1 16 2 sote oil and hgh't CaIb OhC 011 residue meeting the abo Penetration Index 99 06 boiling range specification may be used.

In general, a Suitable filming agent is a Coal r dlstillate These data show that the temperature-susceptibilities of which at least about 90% boils between about 210 C. of the equi-melting residues are decreased as the amount and about 355 C. and having no more than about 10% of oxidized aromatic flux oil residue is increased. residue above 355 C. 20 The standard road binder and that of Example 2 were The resulting blends are useful in all paving applicaapplied to aluminum panels in 0.032 thickness and heated tions for which the standard road tars are used, and proin an Oven at 50 C. The softening points of the residual id resultant coatings hi cure more idl h films were determined at intervals with results shown in standard coatings, have improved (reduced) temperature Table 1 l wsusceptibilities when cured, and result in higher melting TABLE III coatings of characteristically high water resistance and Ex 2 good binding power for mineral aggregates.

The compositions of my invention preferably have dlislg z g ax fl Tfl a 100 m 5 e e'cen i e -nat' e e 40,5 tiuation residues which have p n r i indlc s as e a g tg g gf 1M fined, of above 2, preferably between about 1.0 and softening Pointaiter Heating Time (days) 0 about 0.5 and softening points of at least about C., g i 32 2 preferably between about C. and about C. These 2. 22.3 compositions also preferably have curing rates such that they achieve a softening point of at least about 40 C. in 35 n T i about z t f i gl The above data show that the blended composition of lnch thlcknfiss to 9 am a Ion Example 2, containing oxidized aromatic flux oil residue, following Speclfic examples further mush-ate my although of the same softening point as the Standard RT- lnventlon- 40 8 binder at the time of application, will set or cure more Emmples 1 and 2 rapidly, as indicated by the more rapid attainment of high softening points, than will the standard road tar.

. The oxidized aromatic flux oil residue used in the road y .z ig i g iz z tars of Examples 1 and 2 above was prepared by air i ux O1 resloue m e i i 1 t d p d 45 blowing at 295300 C. and at air rate of 0.03 c.f.m./ with respectlve 0 s ma a gallon of charge, a selected flux oil having the following RT8, and fiuxmg the resultant blends with light carbolic properties. oil residues to RT-8 consistencies. The resulting blends ASTM D 246 distillation percent dist to: had the properties shown in Table 1 below as compared to 210 C 0 0 ASTM D-490 standards and the properties of the standard 50 23 5 C RT8 used. 270 C. 3.4

TABLE 1 ASTM Spec. RT-S Ex. 1 Ex. 2

Percent RT-S 100 67 40. 5 Percent Oxidized Aromatic Flux Oil Residue. 22. 4 40. 5 Percent Light-Carbolic-Oil Residue. 10.6 19 Specific Gravity at 25/25 C., min 1. 200 1. 19 1. 18 Float Test at 32 C., see -120 96. 5 Soluble in CS2, Percent, min 78 91. 9 88. 4 84. 9 Distillation Test (ASTM D-ZO), Percent Distillate by Weight, max;

Residue, Percent 83. 2 77. 9 74.1 Softening Point of Residue (Ring and Ball),

The road tars prepared as described above were then dis- 315 C. 32.7 tilled according to ASTM method D-20 to such end point 355 C. 81.6 temperature as to produce residues melting within the Residue 18.0 range of 57-58 C. (ring and ball). The residues from Specific gravity 25/25" C 1,101

these distillations were then tested for softening point 75 Benzene insolubles 0.5%

The oxidized aromatic [flux oil residue used in Examples 1 and 2 had the following properties:

Softening point (ring and ball) C 73.6 Penetration at:

77 F., 100 g, 5 sec 8 77 F., 200 g., 30 sec 25 115 F., 5 g., sec. 37 Penetration index 0.2 Viscosity SSF at 300 F. sec 220 Benzene insolubles 28.9 Specific gravity 1.230

The light carbolic oil residue used in the above examples had the following properties:

Specific gravity at 25/ 25 C. 1.056 D-246 distillation C.): Percent 0-210 0.0

0355 c 93.3 Residue 5.5

Example 3 An aromatic flux oil having the characteristics set out above was blown with air in a continuous manner at temperatures ranging from 300 C.-400 C. and pressures of 5 0- 66 p.s.i.g. The resultant residue product was mixed continuously with a predetermined blend of normal road tar RT10 and light carbolic oil residue of the character employed in the foregoing examples until the consistency fell within the range of ASTM test 13-490 for RT-lO. The normal tar used and the blend obtained were tested for compliance with ASTM requirements and tor Penetration Index values as shown below.

ASTM Standard Ex. 3

Blend Regular RT-lO, Volume Percent 34. 7 Air Blown Residue, Volume Percent 47. 1 Light Carbolic Oil Residue, Volume Percent i8. 2 Specific Gravity at 25 (3., min. 1.15 1. 232 1. 213 Float at 50 C 75-100 93 97 Soluble CS2, rnin 75 87.2 79. 5 ASTM Distillation (D-20), max:

0l70 C 1. 0 0.0 0. 0 0270 C. 10 3. 0 4. 9 0300 C- 20 9. 1 17. 4 Softening Po t Re all) C 40-70 40. 2 49. 2 Penetration Residue 77 C./100 g./5

sec 67 40 Penetration Index 3. T 1. 9

To characterize the residue used in preparing this blended road tar, small samples of the air-blown residue stream were taken at frequent intervals and combined to form a composite sample respresentative of the airblown residue used in the blend. The composite sample was tested and found to have the following properties:

Sp. Gr. 25/25 C. 1.237

Soft. Pt. ring and ball, F. 166 Distillation ('C.):

First drop 305 0-300, percent 0 0355, percent 43.7 0-360, percent 47.9 Penetration, 77 F./100 g./5 sec. 4

Penetration index 1.0 Benzene isolubles percent 26.2

The standard RT-10 road tar and the oxidized aromatic flux oil residue-containing blend characterized above were applied to a test road on a fall day in Michigan. The standard and experimental road tars were applied from a standard tar spreader at atemperature of 225 F. and at a rate of /4 gallon per square yard. Immediately after application to the road, the tar was covered with 31B cover stone conforming to the specification Percent Passing /s" sieve 100 No. 4 sieve 35-65 N0. 10 sieve ()15 The cover stone was applied at the rate of 30 pounds per square yard and was immediately rolled with a ten ton roller.

Examination of the two test strips the following May on a day when the ambient temperature was in the low s showed that the standard RT10 strip was bleeding badly whereas the strip containing oxidized aromatic flux oil residue binder was satisfactory. Sand was applied to the bleeding RT-lO strip in an amount to furnish 10 pounds of sand per square yard in an attempt to soak up the fluid binder, but was unsuccessful in relieving the condition, and the strip remained very slippery.

The two test strips were examined again, in Septemher, two years after application. The regular RT-lO was found to exhibit some bleeding even after three coverings with sand. The blend containing oxidized aromatic flux oil residue binder had had no sand coverings and showed no evidence of bleeding. Both strips showed good adherence and no signs of failing except for a few cracks.

Examples 4-7 Four road tars were prepared by blending mixtures of the same air-blown aromatic flux oil residue as used in Examples 1 and 2 and a standard RT9 road tar containing between 40% and 60% air-blown residue with different fiuxing oils, including (1) cresote oil, (2) creosote oil distillate to 300 C. and (3) light carbolic oil residue. These tars had the compositions shown in Table IV below.

TABLE IV ASTM BT43 Ex. 4 Ex. 5 Ex. 6 Ex. 7

Air-Blown Residue... Creosote Oil LOO R Creosote Distillate to 300 0 Float- Test at 32 0., seem. CS2 Soluble, Percent, min

Specific Gravity at 25/25 6., min

ASThI D-20 Dist.:

0-270 0., wt. percent, max 0300 6., wt. percent, max S.P. (Ring and Ball) of Residue, O

Penetration of Residue, 77 R,

see Penetration Index 9 The air-blown residue used was the same as that used in Examples 1 and 2 above; the flux oil was the same as that described as starting material in the production of this air-blown residue; the distillate to 300 C. was

1 was air blown with intermittent reflux at a temperature of 232288 C. at an air rate of 100150 c.f.m. for 47 hours thus producing an air-blown residue having the following properties:

prepared by distilling the above flux oil to a vapor tem- 5 perature of 300 C., removing 22.3% of dis i e y Softening point (ring and ball), C 72.0 weight and using the distillate at the flux; the light car- P t ti t; bolic oil used had the following properties: 77 F 100 g, 5 6 Distillation to (1. Percent by weight 5 F 50 5 Sec 34 210 00 Quinoline insoluble, percent by weight 3.2 235 Q6 Benzene insoluble, percent by weight 25.4 270 750 Penetration index 8 315 89.0 3 5 5 9 The air-blown residue thus produced amounted to 6327 Residue 5 gallons, 1345 gallons having been removed as distillate The 0 P O f E p 6 and 7 d of the oil. Aportion ofthis air-blown residue was blended with c m 1 1 HS 5 a standard RT-9 oad ta of the follow 0 t standard RT-9 road tar were subjected to accelerated r r mg pr per 165 curing rate tests as follows: road An 8.00 gram portion of each tar was weighed into ApproximteecompoSition the 11d of a 6-02. Gill style ointment tin, this amount 90% topped tar. produced a film of 0.032 inch thickness corresponding 10% coal tar distillate.

to a road coverage of /3 gal/sq. yd. Nine such tins 6 d ht d f h Float test at 32 0, sec. 154 l Prepare g spfeclmen Specific gravity at /25 C. 1,212 erle5 Was Cafe Y Welg e spefllmefls F P ace 25 C32 Soluble, percent by Weight 89.8 in an oven, equipped with forced air circulation, and distillation percent by Weight (to a C maintained at 50 C. At periodic intervals, one of each 170 0 0 series of specimens was removed from the oven and the 270 softening point determined. The carefully tarred speci- 300 mens were weighed and returned to the oven. 566 u Results: Residue (ring and ball), C. 47.0

TABLE v RT-Q E(. 6 Ex. 7

Elapsed Time Days Percent 8.1. Percent S.P. Percent S.P. wt. Loss (1166B), wt. Loss (lidB), Wt. Loss (IEXZB),

It will be noted from Table V that the road tars conand with a light carbolic oil residue of the properties taining oxidized aromatic flux oil residue showed a much given below more rapid cure in that they attained ring and ball softening points of 40 and above in considerably shorter Llght icarllollc l'esldlle times than did the standard RT-6 road tar. 55 Speclfic gfavlty at 100/ -029 E l 8 d 9 Water, percent by volume 0.0

xamp es D246 distillation, percent by weight (to C.)

Two road tars were prepared by blending air-blown 170 0.0 aromatic flux oil residue with a standard road tar in the 235 2.1 poportions of appoximately 70% and by volume, 270 79.4 respectively, of air-blown residue with 30% and of 300 89.8 the standard road tar and fiuxing with a light carbolic Residue 10.0 oil residue to produce road tars containing 37.9 and 54.6 percent by volume of air-'blown residue. to form two blends as lndlcated below:

An 8044 gallon charge of aromatic flux oil having the following properties Example N0. 8 Flux oil charge: b1

Specific gravity at 100/60 F. 1.099 5; resldue 3699 Water, percent by volume 0.8 R 9 1622 D-246 distillation, percent by weight (to C.): LCOR 1456 270 9.6 Example N0. 9

315 37.9 Gal.

355 70.5 Example No. 8 3777 Residue 28.5 RT9 1644 PHYSICAL CHARACTERISTICS OF ROAD TARS 12 residual films of higher softening points with good adhesion to cover stone and with little tendency to bleed and disengage from the stone aggregate.

Example 10 RT-Q EX. 8 EX. 9 5

T illustrate the superiority of the paving binders of RT 9, percent by vol 100 233 47.2 the invention in producing black bases of higher stabil- Air-blown Residue, percent by vol 54.6 7.9 ity under applied loads than normal road tars, two tars hfig f gfi' fggo gjg iag were prepared, one a Standard RT6, the other a tar of so1upiemos;, ei-e nt 'B,percent wt 89.8 83.6 35.0 m the invention containing 45% of oxidized aromatic flux i ft i g gig gf fgf g 212 L190 198 oil residue, having the constitution and properties set out wt.: below 0 to 170 C 0. 0 o. 0 0. 0

0 to 270 C s. 0 13. 0 10. 7

0 to 300 C 11.4 24. 1 20. 0 BT43 c Examme 10 Residue U01) Ring and Ball Soft. Pt. oi Res, C 47. 0 70.6 61. 4 Formulation;

Standard Road Tar 100 4 2 The standard RT-9 and the tars of the examples were x giihi ofv itann; tested for accelerated cure by the procedure described r 7- Q I o in Examples 4-7 above with the results shown below. il

Specific Gravity (60 F.) 1. 200 1. 189 TABLE VI CS2, Soluble, percent 10. ()0 12. 37

Distillation: q Q 2'2 8'? Time at 50 0., Days oftenmg Pomt (mam re. 4 14.7 -o.s 26.7 are Ex. 8 Ex. 9 38. 0 0

28.4 Each of the tars described above, was mixed in pro- 2%; 22:3 28:2 portions ranging from 96.5% to 94.5% with run-of-bank 4 30 gravel having the following classification analysis using 31%, 333 Standard U.S. Sieves: 26.2 63.2 57.5 4s. 5 es. 0 5s. 4 PaSS1Ilg Percent 231% it? a: 100 35 /a sieve 81.0

It will be noted from Table VI that the road tars of the 38' 3 523 n examples, containing oxidized aromatic flux oil residue 40 sieve a are appreciably faster curing than the Standard RT9 80 Sieve road tar in that they more rapidly attain high softening 200 Sieve points than does the standard road tar.

The three tars described above were applied to ditfer- The black base mlxtures P p and tested ent sections of the same road for test early in November. according to AST Ifist for Stability in the The read had been patched at the Shoulders and was Marshall test machine. In thlS test, gravel and binder swept free of dirt and debris immediately prior to applicamixed at elevated temperature and compacted in fi f h tars. The weather was clear d h d mold to cylindrical test specimens. Test specimens are surface dry. Example 8 was applied first to a portion of Placed in the machine and Subjected to a 10ad pp approximately 1,700 f t This mix was applied at a laterally by means of a constant rate load ack until the temperature f Example 9 was then applied, at maximum load is reached. This value is a measure of a temperature f f the fi t point over a sea the maximum load the material will withstand before and length of approximately 1 f t Regular breaking takes place. Higher values indicate greater was applied, at a temperature f 0 F. to a sueceed resistance to breaking, and thus indicate greater load ing 1,700 ft length bearing capacities. Results of tests on five mixtures conu tars were applied at a coverage f gaheh Per taming different proportions of binder are shown in sq. yd. and /e-inch cover stone was applied in the amount 5 Table VH belowof approximately 30 lbs. per sq. yd. Any tar applied was 7 immediately covered with stone and rolled to embed the TABLE MARSHALL E 551 PM VALLES (ASTM D- stone firmly in the tar. The workmanship was excellent [Maximumloadin pounds] and the application all that could be desired. The initial behavior of was identical- Percent Binder Percent Gravel Standard RTB Example 10 Observation of the stretches of road to which the tars had been applied after elapse of ten months showed that 5 595 958 the section treated with the normal road tar exhibited 2-2 Sig 2g 3%; excessive bleeding and a surface from which a large pro- 0 1 340 1,244 portion of the cover stone had been dislodged. Traffic 965 75? 1,134 areas had smooth oily surfaces.

The section treated with the tar of Example 8 which It will be noted that the black bases made from RT6 had the largest proportion of air-blown residue exhibited tar containing oxidized aromatic flux oil residue binder no signs of wear and no dislodgement of cover stone attain maximum stability with less binder than required whatsoever and no signs of bleeding. for normal road tar, and that the maximum stability even The section treated with the tar of Example 9 was in 79 at this reduced binder content is greater than the maxiexcellent condition with a major proportion of the stone mum that can be achieved with normal road tar. Stated still in place and showed only slight signs of bleeding. another way, using the same amount of paving tar in It will be noted from the above examples that tars conboth cases, the stability of the black base with the pretaining air-blown residue as defined will not only cure oxidized binder is approximately 50% greater than that more rapidly than normal read tars, but will also have using the normal road tar.

While the above describes the preferred embodiments of the invention, it will be understood that departures may be made therefrom within the scope of the specification and claims.

1 claim:

'1. A paving tar composition consisting solely of coal tar derived products, said composition consisting essentially of a mixture of (1) between about 25% and about 75% by volume of a standard coal tar derived road tar as defined in A.S.T.M. standard specification D490, and (2) between about 75% and about 25% by volume of a pitch-like oxidized aromatic coal tar flux oil residue obtained by contacting, with an oxygen-containing gas at temperatures between about 200 C. and about 500 C., a coal tar distillate boiling above about 250 C. selected from the group consisting of light and heavy coal tar oil fractions and residues from redistillation of lighter coal tar distillates and mixtures thereof, said contacting being continued for a time sufiicient to provide a residue having a ring and ball softening point between about 40 C. and about 135 C. and containing between about 15% and about 45% of benzol insoluble compounds and not more than about 5% of quinoline insolubles, and having a penetration index between about and about 1.5, said mixture being blended with (3) a minor amount of a coal tar distillate fiuxing oil of which at least about 90% boils between about 210 C. and about 355 C., sufiicient to bring the consistency of the resulting composition to wit-bin the viscosity requirements of road tar grade tar as specified in ASTM D-490.

2. The composition according to claim 1, wherein the fluxing oil is a light carbolic oil residue.

3. The composition according to claim 1, wherein the standard road tar-oxidized aromatic flux oil residue mixture contains between about 50% and about 75% by volume of oxidized flux oil residue, and wherein the fiuxing oil is a light carbolic oil residue.

4. The composition according to claim 1, wherein the residue obtained by subjecting the said paving tar composition to distillation according to ASTM method D-ZO, has a penetration index of not less than about 1.0, and which residue is capable of setting to a ring and ball softening point of at least about 40 C. in not more than about 5 days when subjected, in a film of about .032 inch thickness to forced air circulation at 50 C.

5. The process for preparing a road tar composition consisting solely of coal tar derived products, said composition meeting the specifications of ASTM D-490 and having a low degree of temperature susceptibility and a rapid curing rate, which comprises blending (1) between about 25 and about 75 by volume of a standard coal tar derived road tar with (2) between about 75% and about 25 by volume of a pitch-like oxidized aromatic flux oil residue obtained by contacting with an oxygencontaining gas at temperatures between about 200 C. and about 500 C. a coal tar distillate boiling above about 250 C. selected from the group consisting of light and heavy coal tar oil fractions and residues from redistillation of lighter coal tar distillates and mixtures thereof, said residue containing between about 15% and about 30% by weight of benzol insoluble compounds and not more than about 5% of quinoline insoluble compounds, and having a ring and ball softening point between about C. and about C., and a penetration index not less than about 1.0 and fluxing the resulting blend with (3) a sufficient quantity of a coal tar distillate of which at least about boils between about 210 C. and about 355 C. and having no more than about 10% residue above 355 C., to bring the consistency of the resulting composition within the viscosity requirements of at least one of the road tar grades as specified as ASTM D-490.

References Cited by the Examiner UNITED STATES PATENTS 2,395,041 2/1946 Fair l9614 2,521,783 9/1950 Farber 106-283 XR 2,701,217 2/1955 Fair l17-113 2,772,219 11/1956 Dunkel et al. 20823 XR 2,826,507 3/1958 Waddill 106284 2,888,357 5/1959 Pittman et al. 106--202 3,173,851 3/1965 King et al 20823 ALEXANDER H. BRODMERKEL,

Primary Examiner.

MORRIS LEIBMAN, Examiner.

I. B. EVANS, Assistant Examiner. 

1. A PAVING TAR COMPOSITION CONSISTING SOLELY OF COAL TAR DERIVED PRODUCTS, SAID COMPOSITION CONSITING ESSENTIALLY OF A MIXTURE OF (1) BETWEEN ABOUT 25% AND ABOUT 75% BY VOLUME OF A STANDARD COAL RAR DERIVED ROAD TAR AS DEFINED IN A.S.T.M. STANDARD SPECIFICATION D-490, AND (2) BETWEEN ABOUT 75% AND ABOUT 25% BY VOLUME OF A PITCH-LIKE OXIDIZED ARMOATIC COAL TAR FLUX OIL RESIDUE OBTAINED BY CONTACTING, WITH AN OXYGEN-CONTAINING GAS AT TEMPERATURES BETWEEN ABOUT 200*C. AND ABOUT 500*C., A COAL TAR DISTILLATE BOILING ABOVE ABOUT 250*C. SELECTED FROM THE GROUP CONSISTING OF LIGHT AND HEAVY COAL TAR OIL FRACTIONS AND RESIDUES FROM REDISTILLATION OF LIGHTER COAL TAR DISTILLATES AND MIXTURES THEREOF, SAID CONTACTING BEING CONTINUED FOR A TIME SUFFICIENT TO PROVIDE A RESIDUE HAVING A RING AND BALL SOFTENING POINT BETWEEN ABOUT 40*C. AND ABOUT 135*C. AND CONTAINING BETWEEN ABOUT 15% AND ABOUT 45% OF BENZOL INSOLUBLE COMPOUNDS AND NOT MORE THAN ABOUT 5% OF QUINOLINE INSOLUBLES, AND HAVING A PENETRATION INDEX BETWEEN ABOUT 0 AND ABOUT -1.5, SAID MIXTURE BEING BLENDED WITH (3) A MINOR AMOUNT OF A COAL TAR DISTILLATE FLUXING OIL OF WHICH AT LEAST ABOUT 90% BOILS BETWEEN ABOUT 210*C. AND ABOUT 355*C., SUFFICIENT TO BRING THE CONSISTENCY OF THE RESULTING COMPOSITION TO WITHIN THE VISOSITY REQUIREMENTS OF ROAD TAR GRADE TAR AS SPECIFIED IN ASTM D-490. 